narrow: get the narrow patterns from the repository object instead of disk

Relying on disk data make the transactionally of this change complicated, so
let us start reading data from other API instead.

mercurial/narrowspec.py

@@ -181,7 +181,7 b' def save(repo, includepats, excludepats)'
 
 
 def copytoworkingcopy(repo):
-    spec = repo.svfs.read(FILENAME)
+    spec = format(*repo.narrowpats)
     repo.vfs.write(DIRSTATE_FILENAME, spec)
 
 
@@ -296,8 +296,9 b' def checkworkingcopynarrowspec(repo):'
     # Avoid infinite recursion when updating the working copy
     if getattr(repo, '_updatingnarrowspec', False):
         return
-    storespec = repo.svfs.tryread(FILENAME)
+    storespec = repo.narrowpats
     wcspec = repo.vfs.tryread(DIRSTATE_FILENAME)
+    wcspec = parseconfig(repo.ui, wcspec)
     if wcspec != storespec:
         raise error.StateError(
             _(b"working copy's narrowspec is stale"),
@@ -312,11 +313,10 b' def updateworkingcopy(repo, assumeclean='
     be deleted. It is then up to the caller to make sure they are clean.
     """
     oldspec = repo.vfs.tryread(DIRSTATE_FILENAME)
-    newspec = repo.svfs.tryread(FILENAME)
+    newincludes, newexcludes = repo.narrowpats
     repo._updatingnarrowspec = True
 
     oldincludes, oldexcludes = parseconfig(repo.ui, oldspec)
-    newincludes, newexcludes = parseconfig(repo.ui, newspec)
     oldmatch = match(repo.root, include=oldincludes, exclude=oldexcludes)
     newmatch = match(repo.root, include=newincludes, exclude=newexcludes)
     addedmatch = matchmod.differencematcher(newmatch, oldmatch)